Hi Charlie

1 Check the volume control icon (bottom right, near clock) Single click
Master vol setting. Is the slider minimised or mute tickbox ticked? If so
untick or move slider to 50%.
1a Double click vol control icon to bring up mixer panel. (select SHOW ALL)
Are any sliders muted or minimised? If so unmute and /or bring up to 50%
level. (Understand you have checked these items, but check them again :-))
(suggest only Line In and Mic Input are muted, You can get distorted sound
or feedback if both line in & line out are active)
1b Check volume slider on your player software. (Muted or minimised? Unmute
or increase to 50%)
2 Do you listen through powered speakers? Are they switched on? (both at the
speaker switch and at the mains and on the PSU) Is the fuse OK? Do you get
voltage out of the PSU? Can you plug phones into a phone socket on the
speakers and listen?
2a Plug the speakers into the phone socket of a walkman. Can you hear?
3 Unplug the speakers at the back of the CPU box and plug in a pair of
phones. Can you hear? If you have a hifi separate cassette recorder try
plugging this into LINE OUT and try to record something and listen through
the recorder phone socket. (make sure LINE IN is muted for this check)
Simply, if you can hear/record test 3, your sound card is ok. Anything not
ok in tests 1 & 2 suggest your speakers/PSU or audio lead are NBG.
I had probs with my onboard sound card and went through this process of
elimination to prove it.
Best of British

Reboot to Safe Mode
Open Device Manager
Remove ALL Sound &Multimedia devices
Remove ALL error-flagged devices
Remove ALL entries in the 'Other Devices' branch - if present
Reboot to Normal Mode - Windows will reinstall the required drivers,
hopefully curing your problem.